An anonymous reader quotes a report from The Guardian: A revolutionary blood test has been shown to diagnose the recurrence of Cancer up to a year in advance of conventional scans in a major lung cancer trial. The test, known as a liquid biopsy, could buy crucial time for doctors by indicating that cancer is growing in the body when tumors are not yet detectable on CT scans and long before the patient becomes aware of physical symptoms. It works by detecting free-floating mutated DNA, released into the bloodstream by dying cancer cells. In the trial of 100 lung cancer patients, scientists saw precipitous rises in tumor DNA in the blood of patients who would go on to relapse months, or even a year, later. In the latest trial, reported in the journal Nature, 100 patients with non-small cell lung cancer were followed from diagnosis through surgery and chemotherapy, having blood tests every six to eight weeks. By analyzing the patchwork of genetic faults in cells across each tumor, scientists created personalized genomic templates for each patient. This was then compared to the DNA floating in their blood, to assess whether a fraction of it matched that seen in their tumor.

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